CY7C68013A, CY7C68014A
CY7C68015A, CY7C68016A
9.17.4 Sequence Diagram of a Single and Burst Asynchronous Write
Figure 9-23. Slave FIFO Asynchronous Write Sequence and Timing Diagram[20]
t
t
t
FAH
t
SFA
SFA
FAH
FIFOADR
t=0
T=0
t
t
t
t
t
t
t
t
WRpwh
WRpwl
WRpwh
WRpwl
WRpwl
WRpwh
WRpwh
WRpwl
SLWR
SLCS
t=3
t =1
T=1
T=4
T=3
T=7
T=6
T=9
t
XFLG
t
XFLG
FLAGS
DATA
t
t
t
t
t
t
t
SFD
t
SFD FDH
SFD FDH
SFD FDH
FDH
N
N+1
N+2
N+3
t=2
T=8
T=2
T=5
t
t
PEpwl
PEpwh
PKTEND
Figure 9-23 shows the timing relationship of the SLAVE FIFO
write in an asynchronous mode. The diagram shows a single
write followed by a burst write of 3 bytes and committing the 4
byte short packet using PKTEND.
The same sequence of events are shown for a burst write and is
indicated by the timing marks of T = 0 through 5.
Note In the burst write mode, after SLWR is deasserted, the data
is written to the FIFO and then the FIFO pointer is incremented
to the next byte in the FIFO. The FIFO pointer is post
incremented.
■ At t = 0 the FIFO address is applied, insuring that it meets the
setup time of tSFA. If SLCS is used, it must also be asserted
(SLCS may be tied low in some applications).
In Figure 9-23 after the four bytes are written to the FIFO and
SLWR is deasserted, the short 4 byte packet can be committed
to the host using the PKTEND. The external device should be
designed to not assert SLWR and the PKTEND signal at the
same time. It should be designed to assert the PKTEND after
SLWR is deasserted and met the minimum deasserted pulse
width. The FIFOADDR lines have to held constant during the
PKTEND assertion.
■ At t = 1 SLWR is asserted. SLWR must meet the minimum
active pulse of tWRpwl and minimum de-active pulse width of
tWRpwh. If the SLCS is used, it must be asserted with SLWR or
before SLWR is asserted.
■ At t = 2, data must be present on the bus tSFD before the
deasserting edge of SLWR.
■ At t = 3, deasserting SLWR causes the data to be written from
the data bus to the FIFO and then increments the FIFO pointer.
The FIFO flag is also updated after tXFLG from the deasserting
edge of SLWR.
Document #: 38-08032 Rev. *V
Page 54 of 66
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